Organic Chemistry (basics) Flashcards
What is a homologous series?
Series of organic compounds having the same functional group but with each successive member differing by CH2
What is a functional group?
Group of atoms responsible for characteristic reactions of a compound
What is a hydrocarbon?
Any compound containing only hydrogen and carbon
What is an aliphatic hydrocarbon?
A straight chained hydrocarbon which can be branched or unbranched
What is an alicyclic hydrocarbon?
Hydrocarbon with a non aromatic ring structure which can also be branched or unbranched
What is an aromatic hydrocarbon?
A hydrocarbon that contains at least one benzene ring
General formula example (decane)
CnH2n+2
Molecular formula example (decane)
C10H22
Empirical formula example (decane)
C5H11
Structural formula example (decane)
CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
Skeletal formula example (decane)
/\/\/\/\/
What is an alkane?
A saturated hydrocarbon containing only C-H bonds
What is the general formula of an alkane?
CnH2n+2
What types of bonds do alkanes have?
Four sigma bonds, either C-H or C-C
What shape and bond angle do alkanes have?
Tetrahedral shape and 109.5* because every carbon atom is surrounded by 4 electron pairs and the shape is caused by the repulsion of these electrons
Why don’t alkanes have a fixed shape?
Because the sigma bonds act as axis for the atoms to rotate around freely
Why is fractional distillation possible in alkanes?
Because the boiling points of the alkanes differ
What are the rules for the boiling points of alkanes?
- Increases as chain length increases as the molecule has a larger surface area so there are more points of contact and so the London forces are stronger and b.p increases
- Decreases as branching increases as the molecules cannot pack together as closely so there are less points of contact which makes the London forces weaker and b.p decreases
Why are alkanes so unreactive?
- C-C and C-H sigma bonds are strong
- C-C bonds are non-polar
- Electronegativity of C and H is so similar
Why are alkanes used as fuel?
Because they are readily available and easy to transport
Can alkanes undergo combustion? If so, what do they produce?
In a plentiful supply of oxygen they can undergo complete combustion to produce CO2 and H20
Equation for butane undergoing combustion
2C4H10(g) + 1302(g) —–> 8CO2(g) + 10H20(g)
General equation for alkane complete combustion
CxHy + (x+y/4)02 —-> XCO2 + y/2H20
When does incomplete combustion occur?
When there is a limited of supply of oxygen
What products can be formed in incomplete combustion?
CO2 + H20 + CO (carbon dioxide) and/or C(soot)
Why is carbon monoxide so dangerous?
It is a colourless, odourless and highly toxic gas, which binds to haemoglobin more readily (higher affinity) than oxygen to form carboxyhaemoglobin. This prevents oxygen from being transported around the body so the victim suffocates to death.
What are structural isomers?
Compounds with the same molecular formula but a different structural formula
What type of reation is combustion?
Oxidation
What are the environmental impacts of soot being formed during incomplete combustion?
- Asthma
- Cancer
- Global dimming
What are the three ways structural isomers can be formed?
- Alkyl groups in different places
- Functional groups bonded to different parts
- Different functional groups
What are the two reactions alkanes can undergo?
- Radical substitution
- Combustion
Describe the sigma bond in an alkane
Sigma bond is a covalent bond which has a direct overlap of the electron clouds of bonding atoms
Why are alkanes insoluble?
Because the hydrogen bonds in water are stronger than London forces and alkanes contain no hydrogen bonds.
What is an addition reaction?
Where 2 reactants join to make 1 product
What is a subsitution reaction?
Where an atom or group of atoms is replaced by a different group of atoms
What is an elimination reaction?
Involved the removal of a smaller molecule from a larger one. 1 reactant molecule forms two products
What is heterolytic fission?
Where one bonding atom receives both electrons from the bonded pair
What is homolytic fission?
Where each bonding atom receives one electron from the bonded pair, forming two radicals
Why do we use radical subsitution?
Because alkanes are very unreactive but if we make radicals then we can get alkanes to react
What are the conditions for radical substitution?
UV light
What are the three main stages of radical substitution?
- Initiation
- Propogation
- Termination